Woodturner's Resource
Woodturner's Resource  
  • Featured Artist    • Websites   Support Wr
Tutorials, Projects & Tips   • Event Calendar   • Tool and Book Store
  Home Page Forum HelpSearch Map TPT Resources LoginRegister
 
Page Index Toggle Pages: 1
Send Topic Print
Greetings from the frozen north, Barrhead, Alberta (Read 330 times)
 
Jeff Hankinson
WR Noob
Offline


Hooked on turning!

Posts: 10

Barrhead, Alberta, Canada
Barrhead
Alberta
Canada

Gender: male

Oneway 16-40
Greetings from the frozen north, Barrhead, Alberta
Feb 18th, 2017 at 2:55pm
 
I'm new to the forum. I've been turning for about three years, mostly vessels with a little spindle work thrown in for practice. There's not a lot of formal instruction locally so I'm largely self taught. I've made most of the mistakes I've heard of and expect to make some no one has heard of. I turn primarily birch, Manitoba maple ( a variety of box elder ), aspen and balsam poplar with a sprinkling of hardwoods like walnut for colour accent. I'm starting to incorporate segmented Turning into my learning curve as well as solid wood projects. The Beads of Courage type programs running in my area present a terrific opportunity to make a large variety of bowls, experimenting with different styles and techniques while providing a very worthwhile place to donate my work. I prefer dry wood turning as opposed to green wood. If I'm in a hurry I can dry a green blank in about three days (rather than waiting for years) in my vacuum kiln - yes three days, it's not a typo error. I figure years are too long to wait... if anyone has questions about vacuum kilns I can certainly try to answer them. Cheers, Jeff
Back to top
  

"Gladly would he learn and gladly teach"
G. Chaucer, Canterbury Tales
 
IP Logged
 
Register To Remove Ads
Ed Weber
WR Global Moderator
WR Patron
*****
Offline



Posts: 4,872

Wilton, California, USA
Wilton
California
USA

Gender: male

JET 1642
Grizzly G0584
Re: Greetings from the frozen north, Barrhead, Alberta
Reply #1 - Feb 18th, 2017 at 3:06pm
 
Jeff Hankinson wrote on Feb 18th, 2017 at 2:55pm:
I've made most of the mistakes I've heard of and expect to make some no one has heard of.


Making your own mistakes is much more fun than copying someone else's  Roll Eyes Smiley

Welcome to the forum
Back to top
  
 
IP Logged
 
Glenn Roberts
WR Supporter
*****
Offline


WR Rocks!

Posts: 229

Walworth, NY, New York, USA
Walworth, NY
New York
USA

Re: Greetings from the frozen north, Barrhead, Alberta
Reply #2 - Feb 18th, 2017 at 9:59pm
 
Jeff, I'm in! Can you describe this magic kiln in detail? I'm a slow learner, so the more detail the better(!).  Having trouble picturing a blank oozing water using subatmospheric pressure, unless voids are in the blank. Does the blank shrink, squeezing the stuff out?
Back to top
  

The older I get, the better I was........
WWW  
IP Logged
 
Jeff Hankinson
WR Noob
Offline


Hooked on turning!

Posts: 10

Barrhead, Alberta, Canada
Barrhead
Alberta
Canada

Gender: male

Oneway 16-40
Re: Vacuum Kiln
Reply #3 - Feb 19th, 2017 at 12:40am
 
Hi Glen. It's not magic, it's physics. Water boils at 100C at sea level, about 2C less at my altitude of 2600 ft. Under a good vacuum, about 26 in mercury, at my altutude, water will boil at 36C or a little less. I posted a fairly complete article on WoW a while back. I didn't invent the idea, people have been playing with it since the 1920s. Turns out to be a victory for the little guy drying small amounts of wood of various dimensions which are just not worth it for wood companies. In brief, my kiln is 18" x 40", 3/8" pipe with a 1/4" steel plate welded on one end and a similar plate to close the other end. I use rubber heat mats to sandwich the green wood, put a temp sensor 1/2 way up the slab or blank, and monitor moisture % remotely. I close up the tank, fire up an old water tolerant vacuum pump and draw a good vacuum as above. I have a drain attached to the tank so the water coming out and condensing on the pipe walls has somewhere to go and generally after 3 or 4 days it's dry. I am sure there is a bit of a moisture gradient going into the wood of up to 12 % but if it's a bowl blank I'm turning that out anyway. Look on Amazon.com for Joshua Salesins book on vacuum kilns. He is soon to publish a new edition I think. My biggest cost was an old vacuum pump of the type he describes. There's lots of pipe in my area. He uses 12" plastic sewer pipe but I felt that was too small for what I planned to turn so 18" for me. A friend built a 20" x 40" kiln. Longer is Not better since wood dries almost completely through the end grain so short thick pieces like turners use is just fine. I would not bother with pieces much longer than the blanks I plan to use. Very gentle on the wood, minimal end checking, occasionally none, unlike any other type of drying. Heat is the enemy so drying a body temp is just right hence the vacuum.
Back to top
  

"Gladly would he learn and gladly teach"
G. Chaucer, Canterbury Tales
 
IP Logged
 
Jeff Hankinson
WR Noob
Offline


Hooked on turning!

Posts: 10

Barrhead, Alberta, Canada
Barrhead
Alberta
Canada

Gender: male

Oneway 16-40
Re: Vacuum kiln continued
Reply #4 - Feb 19th, 2017 at 1:06am
 
The wood does not change in any particular way other than getting a whole lot lighter. A year ago I got some frozen, green balsam poplar of about 60% moisture. I put two slabs of 16" x 16" x 3" in on Jan 1. I took them out Jan 4 at 0% moisture. I collected a couple of gallons of water over that time. Jan 6, 2016 I turned a platter from one of them and it is fine today. No warping or cracking. Air drying from what I've learned is about 99% evaporation from the ends. Hot kilns typically used in the industry speed up the evaporation a lot but still take a long time. The added factor with a vacuum kiln is that the moisture in the wood vapourises, that is, it turns to steam as the heat penetrates the wood and quickly moves out the end grain. That's why it's so darn fast. The low heat is gentle on the wood as well. It is not a violent process, just really fast. The physics was worked out back in the 80s and 90s and is old news now for researchers. The economics were also worked out and don't suit the big companies. I kept my setup simple. 1/2" pipe nipples prethreaded from the hardware store along with gas rated ball valves, some 3/8" reinforced plastic hose, a few connectors, a wood stand and a mechanical timer to automate the whole thing. I use a 18" bicycle inner tube cut around its circumference for a gasket. I ran 110v wire, temp gauge, and a USB cable through the pipe wall and sealed the holes with SealAll. Probably about $500 all in, with $250 of that for the old vacuum pump. That's in Canadian funds, so probably $29.95 US, ha, ha.
Back to top
  

"Gladly would he learn and gladly teach"
G. Chaucer, Canterbury Tales
 
IP Logged
 
Glenn Roberts
WR Supporter
*****
Offline


WR Rocks!

Posts: 229

Walworth, NY, New York, USA
Walworth, NY
New York
USA

Re: Greetings from the frozen north, Barrhead, Alberta
Reply #5 - Feb 19th, 2017 at 6:30am
 
Great reply Jeff - thank you. I assume that the 120v wire is for an internal heater. If so, are you regulating it at a lower temp, say 100F?  Would an inline water trap work to trap the vapor so any pump could be used? Does the drainage drain into a holding tank attached to the bottom of the chamber so that, with the use of 2 valves, the tank could be drained without interrupting the chamber vacuum? And one more: Could a sound electric hot water tank work?\

Thankx,

Glenn
Back to top
  

The older I get, the better I was........
WWW  
IP Logged
 
Jeff Hankinson
WR Noob
Offline


Hooked on turning!

Posts: 10

Barrhead, Alberta, Canada
Barrhead
Alberta
Canada

Gender: male

Oneway 16-40
Re: Greetings from the frozen north, Barrhead, Alberta
Reply #6 - Feb 19th, 2017 at 11:02am
 
Hi again Glenn. Great questions. 110v for the heat mats. These are heavy rubber mats you would normally stand on. They are self regulated not to exceed about 40C so that's easy. I use 3 mats to sandwich two layers of wood. Two 16" x 36" and one 14" x 24" for higher in the tank. These rest on a wood shelf about 1/2 way up the tank. I find the heat transfer to the centre of the wood is better with a mat on each side of the wood. Very thick pieces of 4 to 6 inches take longer to get to adequate internal temp. I did build an inline trap of sorts, 4" pipe stuffed with straws or stainless pot scrubbers and that takes out a lot of the moisture but not all. Not problem for my pump to handle, I change the oil after each run. More effective condensers exist and they are much more expensive. I would not use an expensive Gast type pump for fear of wrecking it. I did also build a drainage tank as you describe. About 2 litres capacity with a valve top and bottom and a crude sight glass. It can be drained easily while the main kiln is running. I also added a solenoid valve on the vacuum line as part of my automation. It is normally closed and when my timer switches on, the valve and the pump activate and run for about 20 min every 3 or 4 hours just to make sure I have maximum vacuum. As for your tank question, atmospheric pressure is about 15 lb per square inch at sea level. I calculated my kiln has more than 10,000 lb pressure on the outside. My 1/4" steel end plate was pushed in about 1/16" on my first test of the kiln. A sound hot water tank would Not work. It would be a real fast redesign opportunity with the first run, turning into a crumpled pop can. I'm not an engineer so I overbuilt the thing on purpose. 3/8" Steel pipe works well in my application. Less wall thickness is risky I feel. My USB cable is for remote monitoring. I put the manufactured ends of the 110 and USB on the inside to avoid a leak source. The USB cable has 4 conductors and a ground. Using 1" nails as pins tapped into the wood in line with the grain, I can monitor up to 4 sites with a common ground. I plug the outside of the USB into the other half of the cable I used inside the kiln and clip the appropriate pairs of wires to my moisture gauge. When they register 10% or lower, I stop the run. Quite honestly I usually stop at 0% or when the readings get irregular since I don't want to get up at night Wink
Back to top
  

"Gladly would he learn and gladly teach"
G. Chaucer, Canterbury Tales
 
IP Logged
 
Len Layman
WR Patron
******
Offline


What have I got into??

Posts: 3,003

Grand Cayman, Cayman Islands
Grand Cayman
Cayman Islands

Gender: male

PM 3520b
Jet 1220
Re: Greetings from the frozen north, Barrhead, Alberta
Reply #7 - Feb 19th, 2017 at 5:35pm
 
Welcome Jeff.  Make yourself at home.
Back to top
  

Len

"Our lives begin to end the day we become silent about things that matter."   MLK
WWW  
IP Logged
 
Register To Remove Ads
Glenn Roberts
WR Supporter
*****
Offline


WR Rocks!

Posts: 229

Walworth, NY, New York, USA
Walworth, NY
New York
USA

Re: Greetings from the frozen north, Barrhead, Alberta
Reply #8 - Feb 19th, 2017 at 6:21pm
 
Jeff, It's tough to crush an egg. I think crushing a water tank would be fun. If the tank works, then I will cut the top off, fabricate latches, and try again.
Thankx for your reply. Very informative.
Back to top
  

The older I get, the better I was........
WWW  
IP Logged
 
Page Index Toggle Pages: 1
Send Topic Print